Hiroshi Imai was born in 1958 at Kobe, Japan. He obtained B.Eng. in Mathematical Engineering, and M.Eng. and D.Eng. in Information Engineering, University of Tokyo in 1981, 1983 and 1986, respectively. In 1986-1990, he was an associate professor of Department of Computer Science and Communication Engineering, Kyushu University. He was also a visiting associate professor at School of Computer Science, McGill University in 1987 and a visiting scientist at IBM T. J. Watson Research Center in 1988. Since 1990, he joined Department of Information Science, University of Tokyo. He is now a professor